The invention relates to frictional surfaces for clutches and brakes and more specifically to a surface configuration for opposing brake and clutch components which exhibits improved static and dynamic frictional characteristics.
There is continuing emphasis directed to improving power and torque transmission levels and performance through frictionally engaging clutch and brake components. This is especially true with regard to automotive related products where volume reduction is necessary due to reduced vehicle size and weight reduction is a constant though increasingly difficult goal.
An area of brake and clutch technology receiving particular attention involves those frictionally coupled energy transmitting components associated with electromagnetic clutches. Such clutches are commonly used to couple and decouple air conditioning compressors from an associated drive member and portions of four-wheel drive schemes from one another. Such electromagnetic clutches are called upon to perform high torque transfer and cycle life but are faced with significant space and cost constraints.
Patent art discloses significant activity in this field. For example, U.S. Pat. No. 2,965,205 teaches a high torque capacity clutch or brake for automatic transmissions. The device includes a frustoconical steel ring having a smooth surface which mates with a similarly configured aluminum ring which is first knurled and then coined such that the knurled surface conforms to the surface of the ring.
U.S. Pat. No. 3,750,788 teaches a clutch or brake configuration wherein a wear resistant material includes a contact face formed exclusively of adjacent isosceles triangular teeth in a circular pattern. The teeth deform the opposed friction lining material and create complementary triangular depressions in a circular pattern.
In U.S. Pat. No. 4,632,236, an electromagnetic clutch includes a frictional surface which is machined to a generally trapezoidal shape. The opposing frictional surface is polished and both surfaces are plated.
U.S. Pat. No. 4,705,973 teaches an electromagnetic clutch wherein the rotor and armature plate both contain spiral, concave grooves and projections. At least one of the surfaces of the rotor or armature plate is plated by a metal having a hardness lower than that of the rotor or armature plate.
Finally, in U.S. Pat. No. 4,727,974, another electromagnetic clutch configuration is disclosed in which one of the clutch surfaces includes a plurality of irregularly shaped projections and the other includes machined and plated concave channels and projections arranged in a spiral pattern.
From a review of the foregoing patents and appreciation of the service life and torque requirements of brakes and clutches, it is apparent that improvement in such devices are both possible and desirable.